Acne vulgaris is reported to be the most common skin disease, affecting approximately eighty percent of the teenage population, and in some cases persisting into the third and fourth decades of life. The pathology of ache is believed to first involve the formation of comedones, which are solid, horny masses of tightly packed keratinized cells which plug follicles. These comedone plugs are first white when formed (whiteheads), but through continued growth and deposition of melanin become blackheads. As the comedo enlarges through continued accumulation of keratinized cells, pressure builds up within the follicles and they eventually rupture, dumping the contents (consisting of horny material, sebum, and bacteria) into the skin. This provokes an inflammatory response; when the rupture is small pustules or pimples develop, and when the follicle completely ruptures cystic nodules result.
It is well known that acne vulgaris can be treated by application of agents which dry and peel the skin to remove keratinous plugs. Well known keratolytic agents are sulfur, resorcinol, benzoyl peroxide, salicylic acid, and hexachlorophene. Benzoyl peroxide is an antimicrobial agent which effectively suppresses the ache bacillus Propionibacteritm aches, an organism which has an important causual role in ache. In addition to being an effective keratolytic agent, salicylic acid also interferes with the formation of blackheads, whiteheads, and the horny masses which clog follicles.
Salicylic acid, benzoyl peroxide, and resorcinol have been incorporated into various anti-acne preparations for years. However, due to the acidic nature of these ingredients, they often exert undesireable effects on the carrier formulation. Salicylic acid, for example, is not water soluble; it can only be solubilized in oils or alcohol. When salicylic acid is incorporated into these preparations at a pH of above 3, it converts to salicylate and causes stability problems in the formulation. Also, salicylic acid is light sensitive above a certain pH. Make-ups made with salicylic acid are known to fade on exposure to light and can be slightly irritating in sensitive skinned individuals who are prone to skin irritations. There is therefore a need for anti-acne preparations having improved stability and aesthetic properties.